The present invention relates generally to systems and methods for maintaining rotating equipment. More particularly, the invention relates to systems and methods for monitoring annular seals between a coupled fluid conduits that rotate relative to each other to identify seal failures.
In applications requiring the transmission of fluid under relatively high pressure, it is sometimes necessary to interconnect a rotating conduit with a stationary conduit, and to provide annular seals therebetween to prevent leakage of the pressurized fluid. One such application is in drilling operations where a wash pipe assembly includes a plurality of axially spaced annular seals radially disposed between a first conduit that rotates relative to a second conduit while pressurized drilling fluid flows through the first and second conduits. Initially, a first seal holds the pressure of the abrasive drilling fluid passing through the assembly. When the first seal eventually wears down and fails, fluid pressure is held by the next seal downstream of the first seal, and so on as drilling operations continue uninterrupted. However, when the final seal fails, drilling fluid may undesirably leak from the assembly, potentially spraying surrounding equipment and personnel. Thus, upon failure of the final seal, drilling operations are typically halted and each of the seals is replaced.
Seals in common use today typically last a few hundred hours, predicting the failure of the final seal is very difficult if not impossible. Unscheduled repairs are more costly than routine maintenance because productive work must cease for an additional period of time. Drilling costs may be thousands of dollars per hour. For a wash pipe seal failure, the nuisance of the fluid spray adds to the work required and to the cost.